Synthesis Of New Wetting Reversing Agent And Its Influence On Seepage Characteristics

Wettability plays an important role in oil recovery. In view of the demands of reducing injecting pressure and enhancing oil recovery for mid-and-low permeability sandstone reservoir, a new trimeric cationic wetting reversal agent called 3RQ was synthesized and its performances were evaluated.The contact angle method was used to measure the 3RQ’s ability of changing wettability of rock/brine/oil system. The results showed that after treated by 3RQ aqueous solution, the contact angle could be reverse from 20°to 165°on water-wetted surface, and from 180°to 60°on oil-wetted surface. To achieve wettability reversal, 3RQ needed smaller amount compared with gemini surfactant and conventional surfactant. And its ability of changing wettability could be blocked by electrolyte.The adsorptive capacity of 3RQ on rock’s surface was measured. The results showed that the adsorption isotherm was belonged to Langmuir adsorption isotherm, and the adsorptive capacity on water-wetted surface was higher than on oil-wetted surface.The adsorptive images of the wettability alteration agents were examined under Atomic Force Microscopy. The research showed that the adsorptive capacity had an directly line with wettability reversal. A mechanism was introduced that wettability reversal on oil-wetted surface was due to oil film shrinking to oil drop after treated by wetting reversal agent.The relative permeability experiments showed that after injecting 3RQ aqueous solution, significant changes happened on the permeability-ratio curve, in particular, the residual oil saturation decreased, and the equal osmotic spot shift to the right, which means the rock become more water-wetted.The reducing injecting pressure experiments showed that 3RQ has the ability to reduce the injection pressure. And the earlier 3RQ can be injected into core, the better the effect.Laboratory displacement experiment result showed that when the rock’s surface is intermediate-wetted, it has the highest water displacement recovery. By using 3RQ can alter the wettability to intermediate-wetted so as to achieve higher water displacement recovery. And 3RQ perform better when the core is oil-wetted.